#!/bin/bash
#===============================================================================
# Copyright 2011 zod.yslin
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# 
# Author: zod.yslin
# Email: 
# File Name: demo.sh
# Description: 
#   Command substitution allows the output of a command to replace the command itself.
# Edit History: 
#   2011-10-04    File created.
#===============================================================================
out=$(ls)
echo $out
out=`ls`
echo $out

file=$0
#$(cat command)  # 執行command中的指令
#$(< command)    # 同上
#The command substitution $(cat file) can be replaced by the equivalent but faster $(< file).
out=$(cat command)
echo $out
out=$(< command)
echo $out

#If the substitution appears within double quotes, word splitting and filename expansion are not performed on the results.
